1. Field of the Invention
The present invention relates to a temperature estimation device estimating a temperature of one power semiconductor chip that is a temperature estimating target and that is included in one or more power semiconductor chips contained in one power semiconductor module included in power semiconductor modules of which number is equal to or larger than the number of motors and that are arranged in the same heat radiator for driving a plurality of motors, respectively. Further, the present invention relates to a motor control device including the temperature estimation device.
2. Description of the Related Art
In order to drive a motor for a feed shaft of a machine tool, a motor for a main shaft of a machine tool, a motor for an arm of an industrial robot, etc., a converter and an inverter are used. The converter and the inverter are each constituted by a power semiconductor module containing at least one power semiconductor chip on which power semiconductors such as a transistor, a diode, and a thyristor are mounted. A temperature of the power semiconductor chip rises by an electric power loss generated at the time of energization of the power semiconductors, and by an electric power loss generated at the time of switching of the power semiconductors. There is a possibility that when a temperature of the power semiconductor chip exceeds a predetermined temperature (e.g., a rated temperature set by a manufacturer of the power semiconductors), an adverse influence (degradation of the power semiconductor chip, breaking of the power semiconductor chip, or the like) of heat on the power semiconductor chip is generated. Accordingly, in order to maintain a temperature of the power semiconductor chip lower than the temperature that can cause the adverse influence of heat on the power semiconductor chip, it is necessary to accurately estimate a temperature of the power semiconductor chip.
For example, as described in Japanese Laid-open Patent Publication No. 2011-36095, conventionally, there was proposed a temperature estimation device estimating a temperature of one power semiconductor chip as a temperature estimating target on the basis of a reference temperature calculated from an electric power loss of all power semiconductor chips in a power semiconductor module, and on the basis of a temperature difference between the reference temperature and a temperature of the power semiconductor module. This temperature estimation device was proposed as a temperature estimation device estimating a temperature of one power semiconductor chip that is a temperature estimating target included in one or more power semiconductor chips contained in one power semiconductor module for driving one motor.
In recent years, in order to reduce a size of a machine tool, an industrial robot or the like, a system which a plurality of inverters, i.e., a plurality of power semiconductor modules, connected in parallel with each other for respectively driving a plurality of motors by one alternating-current (AC) power supply are arranged in the same heat radiator, has been used. In such a system, when a temperature of one power semiconductor chip that is a temperature estimating target is estimated on the basis of a reference temperature calculated from an electric power loss of all power semiconductor chips in one power semiconductor module, and on the basis of a temperature difference between the reference temperature and a temperature of the power semiconductor module in order to estimate the temperature of one power semiconductor chip as the temperature estimating target included in one or more power semiconductor chips contained in one power semiconductor module included in a plurality of the power semiconductor modules, the temperature of one power semiconductor chip that is the temperature estimating target is difficult to accurately estimate. This is because the estimation does not take into consideration influence of heat on the heat radiator caused by all of power semiconductor chips contained in one or more power semiconductor modules other than the power semiconductor module that contains one power semiconductor chip as the temperature estimating target. This influence is an electric power loss generated in one or more power semiconductor modules other than one power semiconductor module that is the temperature estimating target.